Smokin Joe's

[Xrayted]

haha No, the battery fairy comes in and sucks yer soul out while yer sleeping.

An old battery supplier dude once told me that batteries with different mah will deliver different voltage under load. Basically the stronger cells will press voltage back into the lower mah cells in an effort to balance everything out. Might be minuscule but in theory would make for nasty ripple into your ESC. Ripple kills.

I honest to goodness have ZERO data to back that up but I had so much faith in the genius that told me that I never asked again. I asked about battery police coming after me at the time. He saw no humor in my question.

For the record.......I made up the battery fairy. Although.........how do they puff up when not running, not charging, nobody around? Battery fairy?

You are absolutely correct! Mixing different capacity cells is fine for parallel connections but NEVER in series!. Series connected packs must use the exact same capacity cells from the same brand packs and age, as lower capacity cells will naturally have a lower C rating than the bigger capacity cells will. All it takes is one weaker cell with higher IR in the series chain, and that one cell will drag down and damage the other cells that will get hotter having to carry the load it cant, causing their IR start to climb as well, eventually killing the entire pack.

That's how all of our lipos eventually die. It starts with one weaker cells IR starting to climb that slowly kills the others. Mixing different capacity or brand cells with potentially different IRs with each other in series is essentially creating that problem right out of the gate on purpose, which would be a really dumb thing to do

Safe ripple zone is less than 5-7% of the pack voltage at the same measure point, 7-10% means the pack is getting iffy and struggling, and more than 10%-12% means the lipo cannot handle what is being asked of it, and things are in the danger zone for the electronics and the caps ability to keep things from burning. Ripple from any pack is the worst at 50% PWM, and lowest at 100%

[pescador]

You are absolutely correct! Mixing different capacity cells is fine for parallel connections but NEVER in series!. Series connected packs must use the exact same capacity cells from the same brand packs and age, as lower capacity cells will naturally have a lower C rating than the bigger capacity cells will. All it takes is one weaker cell with higher IR in the series chain, and that one cell will drag down and damage the other cells that will get hotter having to carry the load it cant, causing their IR start to climb as well, eventually killing the entire pack.

That's how all of our lipos eventually die. It starts with one weaker cells IR starting to climb that slowly kills the others. Mixing different capacity or brand cells with potentially different IRs with each other in series is essentially creating that problem right out of the gate on purpose, which would be a really dumb thing to do

Safe ripple zone is less than 5-7% of the pack voltage at the same measure point, 7-10% means the pack is getting iffy and struggling, and more than 10%-12% means the lipo cannot handle what is being asked of it, and things are in the danger zone for the electronics and the caps ability to keep things from burning. Ripple from any pack is the worst at 50% PWM, and lowest at 100%

So if the packs are the same manufacturer and capacity but different voltages ie a 4s and a 6s can you run them in series for 10s?


Sent from my iPhone using Tapatalk

[Bande1]

You are absolutely correct! Mixing different capacity cells is fine for parallel connections but NEVER in series!. Series connected packs must use the exact same capacity cells from the same brand packs and age, as lower capacity cells will naturally have a lower C rating than the bigger capacity cells will. All it takes is one weaker cell with higher IR in the series chain, and that one cell will drag down and damage the other cells that will get hotter having to carry the load it cant, causing their IR start to climb as well, eventually killing the entire pack.

That's how all of our lipos eventually die. It starts with one weaker cells IR starting to climb that slowly kills the others. Mixing different capacity or brand cells with potentially different IRs with each other in series is essentially creating that problem right out of the gate on purpose, which would be a really dumb thing to do

Safe ripple zone is less than 5-7% of the pack voltage at the same measure point, 7-10% means the pack is getting iffy and struggling, and more than 10%-12% means the lipo cannot handle what is being asked of it, and things are in the danger zone for the electronics and the caps ability to keep things from burning. Ripple from any pack is the worst at 50% PWM, and lowest at 100%

that happens even within a single pack or in parallel. if a cell is weak and drops much faster than the others it happens no matter how you have them wired. in series you take your smallest pack as the nominal capacity. it is 100% fine to run a 4s and 6s combined to make 10s. even if the mah is different you simply go by the smallest pack.

the only way this can be dangerous is if you are running to LVC as if its an alarm to stop. one pack could be wayyy below 3.2v. you can have that happen with identical batteries and you have forgot to charge one. you should never run to LVC as common practice anyway. every ounce of your boat should be eased into starting with low runtimes and brought in. temps checked, cell voltages checked, systems familiarized, data logs and telemetry employed if possible.

[Bande1]

So if the packs are the same manufacturer and capacity but different voltages ie a 4s and a 6s can you run them in series for 10s?


Sent from my iPhone using Tapatalk

yes. lipos are just a bunch of single cells wired together anyway. they could make 10 cell packs as one battery if they wanted to. you can wire the packs externally no different than manufacturers wiring them internally. the main caveat is if the mah are way different or age. in that case you can still use them together but you need to check cell voltages closely. which you should be doing anyway even with new packs. one battery could be ran lower than 3.2v and cause it to gas. gassing or puffing a battery, if severe enough, can cause a lipo fire by rupturing a cell and exposing it to oxygen. in order for that to happen it has to be extremely severe over-discharging. far lower than even 2.8v.

you should never run any boat more than a minute or so without checking things. ever. you have to get to know the system slowly and safely so you dont burn up motors, esc, batteries.

[Xrayted]

No Bandel. You never want to wire different capacity cells in series with each other. The lower capacity cells, even if the exact same brand pack and actual C rating will automatically have higher IR and less ability to keep up with the higher capacity cells, because IR is a factor of capacity. A 5000 mAh pack with a theoretical C rating of 10 = 50A, but an identical 4000 mAh pack with the same 10C capability will only be able to deliver 40A under the exact same load, so you NEVER mix capacities into the series connection.

Its like purposely building a single pack with multiple "dying" cells compared to the others right out of the box, and it will cause the larger cells to overheat because they will have to be picking up the slack no differently than a single pack with a cell or two that starts to go bad that ultimately causes the pack to have to be replaced. Why would anyone do this on purpose? The classic "weakest link" of a chain applies always when connected in series. These are basic universal laws of electrical physics that govern this, and aren't open for debate.

Parallel is fine mixing capacities because the pack just becomes one big battery of the total capacities, and the IR of the pack goes down as the pack capacity gets bigger as IR is inversely proportional to capacity. The individual cells voltage will all normalize as the higher voltage from one cell flows into any lower voltage cells from one pack to the other.

Nothing like this is happening in series, so capacity must stay the same, and as already stated, ideally you dont want to mix different cells from different brands or different age packs, so that your final series connected packs have cells that are as close to each other performance wise as possible.

I also fly helis, and have one dedicated 150 MPH 14HP speed competition model where we run 12-16S packs using dual 3000-5000 mAh packs in series depending on the voltage used. You wouldn't find anyone that would ever mix capacities in a situation like this, no more than you will ever see any 12S boat guys that know what they doing running mixed capacity packs in series either

[ray schrauwen]

You mean you can't put say 2s and 4s together for 6s in series even if they are matched MAH?

That would explain my smokin' joes entry into Q mono over a decade ago at London pond. Toasted all 4 packs and a SF240. After that I went with 2-6s packs in parallel. 2 sets of 2s + 4S was a bad idea.

[Bande1]

A 5000 mAh pack with a theoretical C rating of 10 = 50A, but an identical 4000 mAh pack with the same 10C capability will only be able to deliver 40A under the exact same load, so you NEVER mix capacities into the series connection.

so first of all you can wild swings in IR in the same pack. or with the same set of packs. what you would do with a situation with one pack having a far lower C/higher IR is prop for the lowest common denominator. 40a would be your target load since it is your weakest battery. If the OP bought two 5s packs he could easily have a cell or two 2-6 milliohms different.

what you do with situations like this is monitor the packs. you do a few laps then check cells. if you see dramatically lower cell or pack you stop. You never run the boat below 20% or 30% even better due to this possibility of cell drop out.

you should be assuming that most lipos are about 15c anyway.

You mean you can't put say 2s and 4s together for 6s in series even if they are matched MAH?

been doing it for 20 years. doing now in my rigger. no different than 3s+3s for 6s, or 2s+2s for 4s. those 6s packs you have are just 1s cells wired in series.

[ray schrauwen]

With a lot less R from wire and 5.5mm bullets.

[Bande1]

With a lot less R from wire and 5.5mm bullets.

you dont use 8awg wire and 8mm bullets?

[ray schrauwen]

Not then I didn't. Batteries were not up to it either.

[Xrayted]

You mean you can't put say 2s and 4s together for 6s in series even if they are matched MAH?

That would explain my smokin' joes entry into Q mono over a decade ago at London pond. Toasted all 4 packs and a SF240. After that I went with 2-6s packs in parallel. 2 sets of 2s + 4S was a bad idea.

Yes, you can wire any combo of packs together in series as long as the capacity is the same between the two packs. You cannot mix capacities when in series. This is electrical physics 101, and anyone claiming otherwise has no understanding of even the most basic principles and universal laws involved here.

[Xrayted]

so first of all you can wild swings in IR in the same pack. or with the same set of packs. what you would do with a situation with one pack having a far lower C/higher IR is prop for the lowest common denominator. 40a would be your target load since it is your weakest battery. If the OP bought two 5s packs he could easily have a cell or two 2-6 milliohms different.

what you do with situations like this is monitor the packs. you do a few laps then check cells. if you see dramatically lower cell or pack you stop. You never run the boat below 20% or 30% even better due to this possibility of cell drop out.

you should be assuming that most lipos are about 15c anyway.



been doing it for 20 years. doing now in my rigger. no different than 3s+3s for 6s, or 2s+2s for 4s. those 6s packs you have are just 1s cells wired in series.

Is is so painful for you to just admit that you might have something to learn? Everything you just wrote is nonsense. No, there aren't "wild swings" of IR within the same pack of 2-6 Mo. 6 Milliohms per cell on a 5000 mAh pack is a pack that needs to be thrown out, and you think a normal lipo has cells that are "swinging wildly" from each other by those amounts?

No such thing is happening in any healthy lipo when in use, and if so then that is a dud pack to begin with and needs to be thrown out. And of course, you use packs that are the same brand and bought at the same time when using two packs in series so that the cell quality and IR of the cells is similar, but YOU NEVER MIX CAPACITIES WHEN WIRING PACKS IN SERIES! IT WILL DAMAGE BOTH BATTERIES!

Your continued claims and rambling defense of doing so otherwise is just making you look foolish. Put your ego aside and do a little research. A simple google search on the subject "should" show you just how silly your constant claims otherwise are, but I feel this still may not matter with you. We are all ignorant of things we dont yet understand, but most will learn and move on. However, there are those that are shown the truth and will still never accept it despite all the evidence otherwise. Those types aren't ignorant, they are fools. Here, I will even help you with the search: https://www.google.com/search?q=can+...t=gws-wiz-serp

Ive said enough hopefully prevent anyone new to all of this from following your terrible advise if they happen to come across this discussion, so I'm out

[fweasel]

Thank you Xrayted. Good link.

[Bande1]

Is is so painful for you to just admit that you might have something to learn? Everything you just wrote is nonsense. No, there aren't "wild swings" of IR within the same pack of 2-6 Mo. 6 Milliohms per cell on a 5000 mAh pack is a pack that needs to be thrown out, and you think a normal lipo has cells that are "swinging wildly" from each other by those amounts?

No such thing is happening in any healthy lipo when in use, and if so then that is a dud pack to begin with and needs to be thrown out. And of course, you use packs that are the same brand and bought at the same time when using two packs in series so that the cell quality and IR of the cells is similar, but YOU NEVER MIX CAPACITIES WHEN WIRING PACKS IN SERIES! IT WILL DAMAGE BOTH BATTERIES!

Your continued claims and rambling defense of doing so otherwise is just making you look foolish. Put your ego aside and do a little research. A simple google search on the subject "should" show you just how silly your constant claims otherwise are, but I feel this still may not matter with you. We are all ignorant of things we dont yet understand, but most will learn and move on. However, there are those that are shown the truth and will still never accept it despite all the evidence otherwise. Those types aren't ignorant, they are fools. Here, I will even help you with the search: https://www.google.com/search?q=can+...t=gws-wiz-serp

Ive said enough hopefully prevent anyone new to all of this from following your terrible advise if they happen to come across this discussion, so I'm out

you're right, series wiring is bad.


I only do 100 laps a week
IMG_20230910_181438.jpg

[Bande1]

Yes, you can wire any combo of packs together in series as long as the capacity is the same between the two packs. You cannot mix capacities when in series. This is electrical physics 101, and anyone claiming otherwise has no understanding of even the most basic principles and universal laws involved here.

now its mah being different. cool story.